Jiaqing Li

Determination of chemical oxygen demand values by a photocatalytic oxidation method using nano-TiO2 film on quartz

A COD measurement by a photocatalytic oxidation method using nano-TiO(2) film was investigated. K(2)Cr(2)O(7) was added into the solution to enhance the efficiency of photocatalytic degradation, and simultaneously K(2)Cr(2)O(7) was reduced to Cr(III) by photogenerated electrons, which were adsorbed on the surface of TiO(2). The measuring principle was based on direct determination of Cr(III) concentration which was proportional to the COD value. Under the optimized experiment condition, the application range was 20-500 mgl(-1), and the detection limit was 20 mgl(-1). The immobilization of photocatalyst on the supports could not only solve the problem of low recovery of the catalyst and hard separation from the solution, but also overcome its shortcoming of poor stability. Applied this method to the determination of real samples, it was found to be rapid and environmentally friendly. Additionally, the method proposed above for determination of COD was in excellent correspondence with values obtained by using the conventional method.

Rh2O3/Ti electrode preparation using laser anneal and its application to the determination of chemical oxygen demand

The method of preparation of a Rh2O3/Ti electrode by using laser calcination and the characterization by x-ray diffractometer were proposed. The electrode, which could develop organic electrocatalytical oxidation, was employed as an amperometric sensor, together with a flow injection analysis, to measure chemical oxygen demand (COD) of waste water in a speedy way. The measuring principle was based on the current responses on the modified electrode which were proportional to the COD value. Under the optimized experimental condition, the linear range was 50–2000 mg l−1, and the detection limit was 20.0 mg l−1 (S/N = 3). This method was successfully applied to determine the COD in samples without pretreatment. It was characterized by short analysis time, simplicity, low environmental impact, limited reagent consumption, easy automation and long lifetime of the sensor. Additionally, the COD values obtained by using the proposed method were within ±5% of those given by the conventional COD method.

Photoelectro-synergistic catalysis combined with a FIA system application on determination of chemical oxygen demand

In this paper, photoelectro-synergistic catalysis oxidation of organics in the water on Ti/TiO(2)/PbO(2) electrode was investigated. The prepared TiO(2) film was investigated with Atomic force micrograph (AFM). Furthermore, the results were compared with those obtained from electrocatalysis (EC) and electro-assisted photocatalysis (PC). The method proposed employed photoelectro-synergistic catalysis (PEC), together with flow injection analysis, to determine the chemical oxygen demand (COD) values. It was shown that the method of photoelectro-synergistic catalysis had lower detection limit (15.0mg l(-1)) and wider linear range (30.0-2500.0mg l(-1)) than the methods of electro-assisted photocatalysis and electrocatalysis. The results obtained by the proposed method and conventional one were compared by carrying out the experiment on 20 wastewater samples and also agreed well by high correlation (R=0.9912).

Determination of chemical oxygen demand using flow injection with Ti/TiO2 electrode prepared by laser anneal

The method of Ti/TiO2 photoelectrode preparation using laser-assisted sol–gel is introduced. The prepared TiO2 film is investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and amperometry, and it illustrates that the TiO2 film mainly consists of anatase TiO2 nanoparticles on its surface and exhibits a superior photocatalytic activity when compared with that calcined by oven. The proposed electrode is employed as a sensor for flow injection analysis (FIA) to determine chemical oxygen demand (COD). The measuring principle is based on the photocurrent responses on the electrode, which are proportional to the COD values. The linear range is 50–1000 mg l−1, and the detection limit is 15 mg l−1 (S/N = 3). This method is characterized by short analysis time, simplicity, low environmental impact and long lifetime of the sensor. Additionally, the COD values obtained from the proposed and the conventional method agree well as demonstrated by the significant correlation between the two sets of COD values (R = 0.9961, N = 20).